Thermodynamic and Kinetic Studies of Uranium and REEs Leaching by Oxalic Acid from Abu-Tartur Phosphate Rock,Western Desert,Egypt

Radiochemistry - Leaching of uranium and REEs with oxalic acid from the Egyptian Abu-Tartur phosphate rock (PR) was studied. The effect exerted on the leaching process by oxalic acid concentration,...     

铀及铀合金防护镀层的研究进展

铀是一种非常重要的战略核材料,纯铀又是化学活性极强的材料,在大气中放置很短的时间就会在其表面产生氧化和腐蚀.因此,对铀材必须实行涂层保护或表面合金化才能增强其抗腐蚀效果.从离子注入、离子镀以及表面合金化处理3方面综述了铀及铀合金的防腐涂层方法的研究.     

U和UO2状态方程研究进展

铀和二氧化铀都是核科学与核工程中的重要材料,长期以来都不缺乏对它们的状态方程的研究.它们生产、存储和使用的环境复杂,涵盖宽温、宽压、强辐照、表面辐射、氦泡演化等极端条件,需要从实验和理论出发获取不同温度和压力下的材料物性,如晶体结构、相变行为、压缩性质、弹性性质与输运性质.此外,它们都属于强关联电子体系,拥有丰富的相图与奇特的物理性质,因此在实验与理论上研究它们的状态方程等物性具有极大的挑战性,该项研究一直属于前沿研究的热点.数十年来,人们采取各种实验手段,对铀和二氧化铀的热力学物性进行了测量;但由于铀及其化合物的特殊性质,相关实验研究工作仍存在一定程度上的困难.而另一方面,自1990年代以来,随着第一性原理方法的发展,使用密度泛函理论(DFT)方法对铀和二氧化铀物理性质展开计算的工作也不断涌现,不仅与实验工作相互验证,而且填补了实验条件无法企及的极端条件下的参数空白.随着计算机软硬件和数值算法的发展,相关DFT方法已经获得了较大突破,对铀和二氧化铀状态方程的描述也更为准确.其中,修正电子多体关联效应的动力学平均场方法(DMFT)以及修正声子振动能的平均场势方法(MFP)等算法是值得研究者进一步关注的.本文就20世纪以来对金属铀和二氧化铀实验和理论状态方程的研究进展进行了梳理,先后针对实验测量和理论计算两方面的晶体结构和相变行为、准静态压缩与冲击绝热压缩曲线、弹性力学、输运性质进行了概括总结,并探讨了二氧化铀晶体缺陷行为的相关研究工作.此外,本文还利用第一性原理方法对铀和二氧化铀的状态方程做了简要的计算,验证了已有公开文献中的结果,这将有助于后续研究.     

铀及其合金表面防护技术的概况及展望

铀作为核能材料,应用很广泛.但铀的化学性质非常活泼,极易腐蚀,研究者们对其表面防护技术进行了许多研究,总结了铀及其合金各种表面防护技术的发展及应用,并对未来的发展趋势进行了展望.     

Special Features in Powder Preparation, Pressing, and Sintering of Uranium Dioxide

Nuclear ceramic grade UO₂ powders are usually prepared by the wet chemical ammonium diuranate route. The powders are pressed and sintered before incorporation into nuclear fuel assemblies. The processing is complex at all stages and the specifications are stringent. In powder preparation, slow addition of the precipitating reagent at a low temperature is recommended. The conditions for the drying of the precipitate, calcination and reduction are chosen to result in an agglomerate free, fine and porous powder that does not require milling or binder addition and is capable of being compacted and sintered to desired density with a homogeneous microstructure. The pressing conditions are chosen to give compacts that are free from defects such as cracking, chipping and end-capping. Sintering conditions are such that desintering, bloating, weathering and nitriding are avoided. Some insights that have been gained in powder preparation, pressing and sintering are presented in this paper. The relationship between powder characteristics and pressing and sintering properties is described.     

Uranium Superconductivity Redux

Since the discovery of heavy-fermion superconductivity in uranium compounds in the early 1980s, other uranium compounds have been discovered that are fully as interesting to study. However, as we look forward in the year 2000, we now have higher-purity, single crystals of the element itself. Preliminary resistivity and ac susceptibility measurements show the improved quality of the samples and thus hold the promise of understanding many aspects of its superconductivity, which have remained untouched for almost 25 years.     

金属铀的氧化腐蚀及防护

铀的氧化腐蚀和防护研究是核材料研究领域的一个重要组成部分。综述了铀在U＋O2体系、U＋H2O(v)体系和U＋H2O（v)＋O2体系中的氧化行为与防护进展，包括氧化腐蚀机理、腐蚀形态、防护措施、防护机理以及防护的发展方向。     

Occurrence of Uranium in Groundwater of Kabirdham,Central India

Radiochemistry - The groundwater quality with respect to uranium and its seasonal variation in Kabirdham district, Chhattisgarh, India was assessed. The uranium content of the collected water...     

Preparation of Pure Uranium,Thorium, and Yttrium Oxides from El-Garra El-Hamra Sulfate Leach Liquor

Radiochemistry - The study deals with separation of uranium, thorium, and yttrium with highest possible purity from El-Garaa El-Hamara sulfate leach liquor. From the latter, almost complete...     

Nonstoichiometry Effect on the Thermodynamic Properties of Uranium Dioxide Containing Alumina, Silica, and Niobia Additions

The structure and oxygen potential of uranium dioxide containing alumina, silica, and niobia additions (a total no greater than 0.4 wt %) are studied with the aim of assessing the doping effect on the properties of oxide fuel. X-ray diffraction examination shows that the sintered material contains a U_0.998Nb_0.002O_{2 + x} solid solution. The effect of Nb doping on the composition dependence of the oxygen potential is examined, and the anion defects present in doped UO₂ are tentatively identified. The results obtained can be used in analyzing the properties of optimized oxide fuel.     

Uranium(VI) complex with m-hydroxybenzoic acid. Synthesis,crystal structure,and spectral properties

A new U(VI) compound with m-hydroxybenzoic acid, HIm[(UO₂)(C₇H₅O³)₃]·2H₂O, was prepared. Its structure was determined by X-ray diffraction analysis and confirmed by the visible and IR spectra. The coordination number of the U atom is 8, with the hydroxyl O atom not involved in coordination with the metal ion. The main structural constituents of the compound are [(UO₂)(C₇H₅O₃)₃]^? anions formed by the sixcoordinate uranyl ion and three hydroxybenzoate ions acting as bidentate ligands. The imidazolium cations participate in hydrogen bonding, linking the adjacent [(UO₂)(C₇H₅O₃)₃]^? anions. The compound contains water molecules of crystallization, also participating in H bonding.     

中国铀矿采冶技术发展与展望

对中国铀矿采冶工业的发展作了全面的回顾,重点介绍了中国铀矿地浸、堆浸、原地爆破浸出技术的研究进展与应用水平;在对中国铀矿采冶形势和存在的问题分析的基础上,结合矿床资源的特点,指出了中国铀矿采冶技术发展的方向。21世纪中国铀矿冶工业面临新的发展机遇和挑战,只有开发新的采、选、冶技术,提高铀资源的利用水平,减少铀矿采冶对环境的影响,才能实现铀矿冶的可持续发展和经济与环境的协调发展。     

Development and Prospect of China Uranium Mining and Metallurgy

The development of industry of uranium mining and metallurgy in China has been reviewed generally, emphasizing on investigation approaches and application levels of uranium mining technologies such as insitu leaching, heap leaching, stope leaching: on the basis of analysis on status of uranium mining and metallurgy and problems existed, also considering the specific features of deposit resources, the development orientation of uranium mining and metallurgy in China is pointed out. The industry of China uranium mining and metallurgy is faced to new opportunity of development and challenge in 21st century, the only way to realize sustainable development of uranium mining and metallurgy and harmonious development between economy and environment is to develop new technology on mining, ore beneficiation and metallurgy, increase the utilization level of uranium resources, low down impact on environment caused by mining and metallurgy.     

水压凿岩机冲击部件结构形状、轴向推力、转钎角度与凿岩效率的试验研究

冲击凿岩能量转换率的高低取决于三个方面,首先是冲锤作用于钎杆的能量,该能量是以压缩波的形式在钎杆中的传递,理想的矩形应力波作用时间长,破岩效率高。根据理想波形和生产工艺条件,采用冲击系统动态反演设计理论,完成了水压凿岩机冲锤(活塞)的理论和结构设计;第二是钎头和孔底岩石的接触状态,轴向推力合适,接触良好,应力波反射小,能量传递效率高;第三是冲击能量和钎头的换位角,通过实验确立了冲击能量和换位角成正比时能量转换率就高的关系。     

Preparation of Powdered Uranium Oxides by Denitration of Nitric Acid Uranium Solutions Using UHF Radiation

Radiochemistry - Denitration of nitric acid uranium solutions under the action of UHF radiation in ambient and reducing atmosphere in the presence of organic reductants containing amino groups...     

Chemical-Spectroscopic Determination of the Isotope Composition and Gravimetric Content of Uranium in Uranium–Aluminum Alloys and Products of Their Processing

Conditions of chemical separation of Al macroamounts and U microamounts, followed by atomic emission spectroscopic determination of the isotope composition and gravimetric content of U, were studied. An algorithm was developed for constructing calibration plots to determine the ²³⁵U/²³⁸U isotope ratio in various samples from nuclear fuel reprocessing. Optimum conditions of the spectral analysis for the U content were found by mathematical design of the experiment: NaCl content 2%, current 18 А, and exposure time 40 s. With the use of these conditions and of a specially developed form of carbon electrode, the uranium detection limit was decreased from 10^–3 to 10^–5%.     

Gas-Phase Volume Oxidation of Uranium Mononitride

Gas-phase volume oxidation (voloxidation) of UN in various atmospheres was studied. Oxidation of compact UN samples under the conditions characteristic of the voloxidation of the oxide fuel leads to the formation of uranium oxides. The use of the oxygen-containing atmosphere leads to the predominant formation of U₃O₈, and the use of water vapor, to the formation of UO₂. The major gaseous nitrogen-containing conversion product is, apparently, N₂. The use of the alternative oxidizing atmosphere based on NO_x gases does not allow the conversion to be performed at a lower temperature. In this case, both UO₃ and UO₂(NO₃)₂ hydrates are formed. The maximal degree of the UN conversion to water-soluble compounds, equal to ～80%, is reached at the process temperature of ～565 K.